Upstream classifier for a multi-separator

ABSTRACT

Apparatus is described for classifying particulate matter of different densities that is entrained in a fluid flow stream and for selectively proportioning, on a density basis, the flow of particles to the inlets of plural separators. The apparatus includes a bend section of a duct system in which the particles are initially concentrated and a baffle disposed immediately downstream of the bend section which is operative to deflect the particles transversely across the path of the gas component. The particles are operated on by the gas to deliver the finer particles to one separator and the more coarse particles to the other separator.

United States Patent 9 [191 Musto UPSTREAM CLASSIFIER FOR A MULTl-SEPARATOR [75] Inventor: Richard Leopold Musto,

Homewood, 111.

[73] Assignee: Combustion Engineering, Inc.,

Windsor, Conn.

22 Filed: Dec. 15,1972

21 Appl. No; 315,688

[ 1 Feb. 11, 1975 Cowher 209/135 Peterson et a1. 209/144 X [57] ABSTRACT Apparatus is described for classifying particulate matter of different densities that is entrained in a fluid flow stream and for selectively proportioning, on a density basis, the flow of particles to the inlets of plural separators. The apparatus includes a bend section of a duct system in which the particles are initially concentrated and a baffle disposed immediately downstream of the bend section which is operative to deflect the particles transversely across the path of the gas component. The particles are operated on by the gas to deliver the finer particles to one separator and the more coarse particles to the other separator.

7 Claims, 5 Drawing Figures PATENTED FEB] 1 i975 3.865.242

SHEET 10F 3- PATENTEU F591 1 I975 SHEEl 3 OF 3 FIG.

FIG.

UPSTREAM CLASSIFIER FOR A MULTI-SEPARATOR BACKGROUND OF THE INVENTION In flash drying systems wet material is introduced to a hot gas stream in which rapid evaporation of the moisture entrained in the material occurs. Following the drying operation the particulate material must be separated from the gas stream by passing the mixture through a mechanical separator, or the like. In conventional prior art systems the flow stream is conveyed in a duct where most of the drying occurs. The discharge end of the duct connects with a separator, usually of the cyclone type, in which the dried material is separated from the gas stream and discharged as finished product.

In the flash drying of many materials, the wet feed is composed of particles having a multitude of different sizes as well as agglomerates of the smaller sized particles. The smaller the particle or agglomerate, the more rapid is the rate of drying. Since all of the particles and agglomerates are contained in the gas stream an equal amount of time, the smaller elements usually achieve a greater degree of dryness than the larger elements. This results in a finished product which includes some particles that have not been completely dried and others that may be overly dried. If the residence time or operating temperatures are increased to complete the drying of the larger elements, the finer elements obviously may become overly dried thereby subjecting the material to degradation or decomposition. In extreme cases the finer material could even be caused to burn creating the hazard of fire in the duct system.

Attempts have been made to alleviate this problem by classifying the flow stream into two fractions according to particle size or density characteristics and passing each fraction to one of a plurality of parallelly connected separators for processing. The less dense fraction will be, by deduction, comprised of finer and therefore drier particulate matter, which after separation from the gas stream, may be discharged as finished product. The other fraction being of greater density due to its composition of larger and, therefore wetter particles, will be separated from the gas in the other separator with the particles then being capable of being returned to the drier for recycling through the system. Prior art systems seeking to accomplish the above result have utilized a duct having a bend section therein upstream of the separator inlets whereby the more dense solids particles in the flow stream are caused to migrate toward the outside of the bend by centrifugal action. An adjustable skimmer or divider plate is disposed within the duct between the discharge end of the bend section and the separators and operates to direct particles of different size or density to the inlets of the respective separators.

Such systems have met with only limited success primarily due to the fact that the particulate component of the flow stream, being made up of particles of sev eral different sizes or densities, does not have sufficient residence time within the bend section to permit adequate stratification of the particles into layers according to size or density. Thus, where a skimmer or divider plate is employed, accurate separation of the finer elemerits from the more coarse elements is not possible.

It is toward the improvement of such systems, therefore, that the present invention is directed.

III

SUMMARY OF THE INVENTION According to the present invention there is provided a multi-separator processing organization for effectively classifying a flow stream containing particulate matter of various densities into plural fractions, according to the density characteristics of each. The duct conveying the flowing mixture contains a bend section within which the solids particles are caused by centrifugal action to migrate toward the outer boundary thereof. An adjustable deflector baffle is disposed immediately downstream of the bend section and operates on the flowing media to deflect the particles across the gas stream. The gas operates on the particles to convey the finer,.drier component toward the inlet of one of the separators, while the more coarse, wetter component, having greater inertia than the finer com-. ponent, and therefore less subject to the'force of the flowing gas, is directed to the inlet of the other separator. By adjusting the position of the deflector baffle with respect to the flow stream, adjustments can be made in the proportion of particulate matter directed to each separator.

It is accordingly an object of the present invention to provide a simple, yet effective organization operative to selectively feed material to a multi-separator processing system according to particle density.

Another object of the invention is to provide an adjustable control in multi-separator processing systems for initial classification of feed material prior to its admission to the respective separators.

Another object of the invention is to provide a control of the described type in which adjustments can be accurately effected'from outside the apparatus.

Another object of the invention is to provide flash drying systems with means for producing a uniformly dry product and thereby eliminate degradation of the product by overdrying or underdrying the same.

Another object of the invention is to increase the thermal efflciency of flash drying systems by reducing the amount of sensible heat transferred to the product.

Another object of the invention is to increase the thermal efficiency of flash drying systems utilizing lower gas exit temperatures.

Other objects and advantages of the present invention will become evident when the following description is read in conjunction with the attached drawings.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a partial perspective representation of a flash drying system employing two separators and feed DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings, there is illustrated the discharge end 10 of apparatus in which solid particles are rapidly dried by direct contact with hot gases. Such systems are commonly referred to as flash drying systems. The entire system is not described here as it is not germane to the invention.- Only so much is disclosed as is necessary for a complete understanding of the invention. For a detailed description of a typical flash drying system similar to that involved here, reference can be made to US. Pat. No. 2,350,162 issued May 30, 1944 to Charles W. Gordon.

Going now to FIG. 1, there is shown processing apparatus comprising a pair of parallelly connected cyclone separators 12 and 14 having particle discharge conduits, 16 and 18 respectively, connecting at their lower ends and gas discharge conduits 20 that extend from their upper ends. Each of the conduits 20 is provided with a damper 22 to regulate the gas flow directed through the respective separators 12 and 14. The inlets 24 and 26 of the respective separators are rectangular in section and are disposed in contiguous juxtaposition with respect to one another. The two inlets are separated by divider plates 27 and each connect tangentially with the interiors of the respective separators.

An elongated duct here shown as being generally rectangular in section, connects in common with the inlets 24 and 26 of the separator 12 and 14 and serves to convey a mixture of hot gas with entrained particulate matter to the separators. The particles entrained in the gas are of varying degrees of size or density and include agglomerated particles. The duct includes an upstanding section 28, a relatively long radius bend section and a distribution section 32. The upstanding section 28 communicates at one end with a source of hot gas flowing at a relatively high velocity and a separate source of particulate matter to be dried. Neither of these sources are shown in the drawing. In systems of the type described, the gas velocities may be in the range of 300 to 5,000 feet per minute. The bend section 30 which is preferably approximately ninety degrees in extent is attached at one end to the upstanding sections 28 by means of a transition section (FIG. 2).

The distribution section 32 connects between the downstream end of the bend section 30 and the contiguous inlets 24 and 26 of the separators 12 and 14. It comprises top and bottom plates, 35 and 36 respectively, and laterally opposed side plates 38 As shown, the plates 35, 36- and 38 are all trapezoidally shaped with the top and bottom plates 35 and 36 being outwardly divergent from the downstream endof the bend section 30 and the side plates 38 being outwardly convergent therefrom. The plates are sized and arranged to define a flow path from one end of the distribution section 32 to the other which is of substantially uniform cross-sectional area so as to maintain the flow velocity therethrough substantially constant.

According to the invention, the interior of the distribution section 32 is provided with a pivotally mounted baffle plate 40 which is adapted to be adjustably positioned within the section and which operates to deflect the fluid flowing therethrough as hereinafter explained. In the preferred arrangement the baffle plate 40 termed the particle deflector plate is connected for simultaneous adjustment with a second baffle plate 42 as shown and described herein. It should be appreciated however that the present invention does not require the interconnection between the two plates or even that the second plate be employed at all. The baffle plates 40 and 42 are fixedly attached to each of two vertically spaced pivot pins 44 and 46 whose ends are rotatably supported within bearing pads 48 attached to the side 4 plates 38 of the distribution section 32. As shown in FIGS. 2, 4 and 5 the baffle plates 40 and 42 are disposed such that their pivot ends are positioned closely adjacent to the dowstream end of the bend section 30 and generally tangentially to the radially inner and outer sides thereof. The baffle plates 40 and 42 are substantially trapezoidally shaped to conform generally to the interior of the distribution section 32 and have their side edges closely spaced from the inner surfaces of the side plates 38 thereof.

Means are provided to adjustably position the baffle plates 40 and 42 within the section 32. Such means include a pair of operating levers 50 and 52 that are rigidly connected at one of their respective ends to each of the pivot pins 44 and 46. The other ends of the levers 50 and -52 are mutually connected by a link 54 that serves to operate the levers, and thereby to rotate the plates in unison. In the described arrangement an index plate 56 is provided for positioning the baffle plates in preselected positions. It includes a number of spaced recesses 57 adapted to selectively receive the tip of an adjustment stud 58 that is threadedly secured to the lever 52.

The operation of the herein described apparatus is as follows. A flow stream comprising a mixture of heating gas and entrained particulate matter of various particle size and densities, such as fines and coarse particles of organic material, is admitted to the duct system. The temperature of the gas is such as will accomplish drying of the finer particles in the mixture to an acceptable degree of dryness in a single pass through the duct system. The more coarse particles and agglomerates are of a greater degree of wetness and therefore incapable of being acceptably dried as finished product in one pass through the system.

The position of the dampers 22 in the gas discharge conduits 20 are adjusted such that the flow of gases entering the inlets 24 and 26 of the respective separators 12 and 14 is approximately equal and the baffle plates 40 and 42 in the distribution section 32 are moved to a position similar to that shown in FIG. 4. With the baffle plates so disposed the particle deflector plate 40 is caused to extend at an oblique angle part way across the interior of the distribution section 32 so as to obstruct direct entry of the flowing mixture into the inlet opening 24.

As the flow stream passes through the upstanding section 28 of the duct, the fine and coarse particles are disposed in a random orientation with respect to one another. As the mixture passes through the bend section 30, however, all of the particles are caused to migrate under the influence of centrifugal forces generated therein toward the radially outer boundary of the section with the more coarse particles comprising the boundary layer and the finer particles tending to occupy the region radially inwardly therefrom. The gaseous fluid, being the. least dense element and, therefore, least effected by centrifugal forces undergoes no appreciable radial migration. There results a relatively thin continuous sheet or ribbon of particulate material that flows through the duct 28 adjacent the radially outer boundary thereof.

Upon exiting the bend section 30, the flow stream engages the surface of the particle deflector plate 40 which deflects the gas and sheet of particulate material obliquely downwardly toward the inlet 26 of the separator 14. The dampers 22 being set to pass half the gas flow through each separator inlet 24 and 26 causes that portion which is to enter the separator inlet 24 to be diverted around the free end of the baffle plate 40 and pass transversely through the sheet of concentrated particulate material as indicated by the arrows in FIG. 4. in so passing through the sheet of particles, the flowing gas entrains the drier, and thereby finer particles and conveys them through the inlet 24 into the separator 12 where the particles are removed from the gas and discharged through conduit 16 as finished product. The separated gas leaves separator 12 through the gas discharge conduit 20 associated therewith.

The more coarse, and therefore wetter particles and agglomerates in the concentrated sheet of particulate material having greater inertia than the finer particles are less effected by the fluid that passes transversely through the flowing sheet and thus continue on into the inlet 26 of separator 14. Within the separator 14 these particles are separated from the gas, with the gaseous component exiting the separator through conduit 20 and the particles being discharged through conduit 18 by means of which they are returned to the drying system (not shown) for further exposure to the drying gases. Following this the particles are returned to the duct system for further processing as previously described. This procedure is repeated until the large particles are sufficiently dry and fine to be conveyed through the inlet 24 into the separator 12 for ultimate discharge as finished product.

By varying the angular position of the deflector plate 40 the division of material admitted to the respective separators can be adjusted. Raising the free end of the particledeflector plate by adjusting the setting of i the stud 58 in the index plate 56 will result in particles of greater density or coarseness being caused to enter the inlet 24 of the separator 12 from whence they will be discharged ultimately as finished product. Conversely, lowering the free end of the plate 40 decreases the size of the particles-passing into the separator 12.

The lower plate 42 is operative when it is desired to terminate operation and flush the system of particulate matter. This is accomplished by first halting the admission of particulate solids to the duct system while continuing the flow of gas therethrough. The baffle plates 40 and 42 in the distribution section 32 are rotated until the free end of the lower plate 42 is moved to its uppermostposition as shown in FIG. 5. With the plate so disposed the particle deflector plate 40 is withdrawn from the flow path of the sheet of concentrated solid particles exiting the bend section 30 of the duct system and the lower plate 42 is in a position to intercept part of the gas flow. With the deflector plate '40 in its withdrawn position, the particulate material is caused to be directed by inertia into the inlet opening 24 of the separator 12. The direction of the particulate material into the inlet 24 is augmented by the deflection of part of the gas flow by the lower baffle plate 42 toward the inlet opening 24 as indicated by the arrows in FIG. 5. The particulate material is separated from the gas within the separator 12 and discharged from the system through conduit 16. This procedure is continued until all particles are withdrawn from the system.

From the foregoing it will be appreciated that the present invention provides apparatus that more effectively classifies particulate matter entrained in a gas stream according to density differences. Because classifying is achieved by a fluid separation process rather than by mechanical separation greater separation efficiencies are obtained. While the invention is not limited in application to flash drying systems described herein, when utilized in such systems it is effective to produce a product of more uniform dryness thereby reducing the possibility of degradation of product caused by overdrying or underdrying thereof. Additionally, its use increases the thermal efficiency of the drying system by reducing the gas discharge temperature and the amount of sensible heat transferred to the product and achieves a concomitant reduction in drying gas exit temperatures.

It will be understood that various changes in the details, materials, and arrangements of parts which have been herein described and illustrated in order to explain the nature of the invention, may be made by its skill in the art within the principle and scope of the invention as expressed in the appended claims.

l claim:

1. A method of separating a mixture of fine and coarse solids particles entrained in a fluid stream flowing through a duct for delivery to separate receptacles, comprising the steps of:

a. concentrating the combined fine and coarse solids particles in one region of the stream as a continuous, moving sheet of material;

b. directing said sheet of material toward one of said receptacles;

c. diverting a portion of the fluid from said stream through said region and into the other of said receptacles and passing the remaining portion to said one receptacle while preventing a substantial reduction in the flow velocity of said flowing .fluid whereby the fine solids particles are removed from said sheet of material and delivered to said other receptacle.

2. The method of claim 1 in which said sheet of concentrated particles is directed toward said one receptacle by impinging said particles upon a baffle plate inclined transversely of the fluid flow path.

3. The method of claim 1 in which said combined fine and coarse solids particles are concentrated into a sheet of material by flowing the mixture along an arcuate path. I i

4. Apparatus for separating a flowing mixture of fine and coarse particles entrained in a fluid for delivery to separate receptacles, comprising:

a. duct means, substantially rectangular-in cross section, including a series connected bend section and distribution section upstream of said receptacles;

b. means forming a pair of inlet openings each mom of said receptacles communicating in common with the downstream end of said distribution section at vertically spaced, side-by-side positions therein;

c. said bend section connecting at the upstream end of said distribution section and including an arcuate bend of sufficient extent to concentrate said fine and coarse particles by centrifugal action in a continuous sheet adjacent one vertical side of said bend section;

d. means in said distribution section for maintaining the fluid flow velocity therethrough substantially constant; v

e. a baffle plate disposed in said distribution section extending obliquely of the flow path therethrough from said one vertical side outwardly in the direction of fluid flow for directing said sheet of concen- 8 spaced positions within said distribution section.

6. Apparatus as recited in claim 4 including a second baffle plate pivotally mounted at one end adjacent said opposite side of said duct and its free end positionable between said sides of said duct to present a surface inclined in the direction the inlet opening adjacent said one vertical side when said other baffle plate is withdrawn from its operative position.

7. Apparatus as recited in claim 6 in which said baffle plates are connected for parallel pivotal movement. 

1. A method of separating a mixture of fine and coarse solids particles entrained in a fluid stream flowing through a duct for delivery to separate receptacles, comprising the steps of: a. concentrating the combined fine and coarse solids particles in one region of the stream as a continuous, moving sheet of material; b. directing said sheet of material toward one of said receptacles; c. diverting a portion of the fluid from said stream through said region and into the other of said receptacles and pAssing the remaining portion to said one receptacle while preventing a substantial reduction in the flow velocity of said flowing fluid whereby the fine solids particles are removed from said sheet of material and delivered to said other receptacle.
 2. The method of claim 1 in which said sheet of concentrated particles is directed toward said one receptacle by impinging said particles upon a baffle plate inclined transversely of the fluid flow path.
 3. The method of claim 1 in which said combined fine and coarse solids particles are concentrated into a sheet of material by flowing the mixture along an arcuate path.
 4. Apparatus for separating a flowing mixture of fine and coarse particles entrained in a fluid for delivery to separate receptacles, comprising: a. duct means, substantially rectangular in cross section, including a series connected bend section and distribution section upstream of said receptacles; b. means forming a pair of inlet openings each to one of said receptacles communicating in common with the downstream end of said distribution section at vertically spaced, side-by-side positions therein; c. said bend section connecting at the upstream end of said distribution section and including an arcuate bend of sufficient extent to concentrate said fine and coarse particles by centrifugal action in a continuous sheet adjacent one vertical side of said bend section; d. means in said distribution section for maintaining the fluid flow velocity therethrough substantially constant; e. a baffle plate disposed in said distribution section extending obliquely of the flow path therethrough from said one vertical side outwardly in the direction of fluid flow for directing said sheet of concentrated material in the direction of the inlet opening adjacent the opposite vertical side of said distribution section; and f. means for passing said fluid through both of said inlet openings with a portion thereof passing through said sheet of concentrated material and being operative to conduct the fine particles therein into the inlet opening adjacent said one vertical side of said distribution section.
 5. Apparatus as recited in claim 4 in which said baffle plate is pivotally attached at its end adjacent said one vertical side for adjustment to respective angularly spaced positions within said distribution section.
 6. Apparatus as recited in claim 4 including a second baffle plate pivotally mounted at one end adjacent said opposite side of said duct and its free end positionable between said sides of said duct to present a surface inclined in the direction the inlet opening adjacent said one vertical side when said other baffle plate is withdrawn from its operative position.
 7. Apparatus as recited in claim 6 in which said baffle plates are connected for parallel pivotal movement. 